linux-kernel - Re: [PATCH 1/1 next] tools build: Remove the libunwind feature tests from the ones detected when test-all.o builds

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Message-ID: <Z9tBnDYy0slX2xh7@google.com>
Date: Wed, 19 Mar 2025 15:13:48 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Jiri Olsa <olsajiri@...il.com>
Cc: Quentin Monnet <qmo@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	James Clark <james.clark@...aro.org>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org, bpf@...r.kernel.org,
	linux-trace-devel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 1/1 next] tools build: Remove the libunwind feature tests
 from the ones detected when test-all.o builds

Hi Jiri,

On Wed, Mar 19, 2025 at 10:47:40AM +0100, Jiri Olsa wrote:
> On Tue, Mar 18, 2025 at 04:51:53PM -0700, Namhyung Kim wrote:
> > Hello,
> > 
> > On Mon, Mar 17, 2025 at 09:19:22PM +0000, Quentin Monnet wrote:
> > > 2025-03-17 10:16 UTC-0700 ~ Ian Rogers <irogers@...gle.com>
> > > > On Mon, Mar 17, 2025 at 10:06 AM Namhyung Kim <namhyung@...nel.org> wrote:
> > > >>
> > > >> Hello,
> > > >>
> > > >> On Mon, Mar 17, 2025 at 09:10:29AM -0700, Ian Rogers wrote:
> > > >>> On Wed, Dec 11, 2024 at 7:45 AM Arnaldo Carvalho de Melo
> > > >>> <acme@...nel.org> wrote:
> > > >>>>
> > > >>>> We have a tools/build/feature/test-all.c that has the most common set of
> > > >>>> features that perf uses and are expected to have its development files
> > > >>>> available when building perf.
> > > >>>>
> > > >>>> When we made libwunwind opt-in we forgot to remove them from the list of
> > > >>>> features that are assumed to be available when test-all.c builds, remove
> > > >>>> them.
> > > >>>>
> > > >>>> Before this patch:
> > > >>>>
> > > >>>>   $ rm -rf /tmp/b ; mkdir /tmp/b ; make -C tools/perf O=/tmp/b feature-dump ; grep feature-libunwind-aarch64= /tmp/b/FEATURE-DUMP
> > > >>>>   feature-libunwind-aarch64=1
> > > >>>>   $
> > > >>>>
> > > >>>> Even tho this not being test built and those header files being
> > > >>>> available:
> > > >>>>
> > > >>>>   $ head -5 tools/build/feature/test-libunwind-aarch64.c
> > > >>>>   // SPDX-License-Identifier: GPL-2.0
> > > >>>>   #include <libunwind-aarch64.h>
> > > >>>>   #include <stdlib.h>
> > > >>>>
> > > >>>>   extern int UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
> > > >>>>   $
> > > >>>>
> > > >>>> After this patch:
> > > >>>>
> > > >>>>   $ grep feature-libunwind- /tmp/b/FEATURE-DUMP
> > > >>>>   $
> > > >>>>
> > > >>>> Now an audit on what is being enabled when test-all.c builds will be
> > > >>>> performed.
> > > >>>>
> > > >>>> Fixes: 176c9d1e6a06f2fa ("tools features: Don't check for libunwind devel files by default")
> > > >>>> Cc: Adrian Hunter <adrian.hunter@...el.com>
> > > >>>> Cc: Ian Rogers <irogers@...gle.com>
> > > >>>> Cc: James Clark <james.clark@...aro.org>
> > > >>>> Cc: Jiri Olsa <jolsa@...nel.org>
> > > >>>> Cc: Kan Liang <kan.liang@...ux.intel.com>
> > > >>>> Cc: Namhyung Kim <namhyung@...nel.org>
> > > >>>> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> > > >>>
> > > >>> Sorry for the delay on this.
> > > >>>
> > > >>> Reviewed-by: Ian Rogers <irogers@...gle.com>
> > > >>
> > > >> Thanks for the review, but I think this part is used by other tools like
> > > >> BPF and tracing.  It'd be nice to get reviews from them.
> > > > 
> > > > Sgtm. The patch hasn't had attention for 3 months. A quick grep for
> > > > "unwind" and "UNW_" shows only use in perf and the feature tests.
> > > > 
> > > > Thanks,
> > > > Ian
> > > 
> > > 
> > > Indeed, bpftool does not rely on libunwind, and I don't remember other
> > > BPF components doing so, either.
> > 
> > Right, but my concern was about the feature test itself and the related
> > changes in the build files.
> > 
> > Can I get your Acked-by then?
> 
> hi,
> I might be missing something, but I see following commit in git already:
>   b40fbeb0b1cd tools build: Remove the libunwind feature tests from the ones detected when test-all.o builds

Oops, thanks for checking this.

I was confused by Ian's late reply and thought it belongs to this
cycle. :)  Yep, it's already merged in the previous cycle.

Sorry for the noise.
Namhyung